The present invention relates to a color recording apparatus comprising a recording medium on which a plurality of images in different colors such as yellow, magenta, cyanogen, and black are overlappingly recorded to form a multicolored image.
Also, the present invention relates to a color recording apparatus such as a color copying apparatus or a color printer in which a multicolored image is formed by a switch back type image transferring mechanism.
Further, the present invention relates to a color recording apparatus in which a multicolored image is formed on a paper in such a way that a plurality of images analyzed in a different color, respectively, are formed on a image carrier one after another and after that the images are overlappingly transferred from the image carrier to the paper which is supported and conveyed by a paper conveyor means which is movable forward and backward and which means also movable toward and away from the image carrier.
In accordance with one type of conventional color copying apparatuses, a multicolored image is formed on a record paper by overlapping and transferring a plurality of different color toner images comprising a group of a yellow image, a magenta image, and a cyanogen image or a group of a yellow image, a magenta image, cyanogen image and a black image. To be more precise, first, an electrostatic latent image corresponding to a yellow component of an original image to be copied is formed and developed by a yellow toner, then the developed yellow color toner image is transferred to a record paper. Second, an electrostatic latent image corresponding to a magenta component of the original image is formed and developed by a magenta color toner. The developed magenta toner image is transferred to the record paper overlapping the yellow toner image. After that, an electrostatic latent image corresponding to a cyanogen component of the original image is formed and developed by a cyanogen color toner. The developed cyanogen color toner image is transferred to the record paper on which the yellow image and the magenta image are overlappingly formed. If the copying apparatus comprises a black toner developer, an electrostatic latent image corresponding to a black component of the original image is formed and developed by the black toner. The black toner image is transferred to the record paper overlapping the preceding three different color images.
With the above mentioned method for recording the multicolored image, it is important to precisely align the different color toner images with each other on the record paper in order to obtain a clear color image.
For example, Japanese Unexamined Patent Publication No. 62-239178 discloses a flash exposure type color record apparatus which comprises a photoconductor belt arranged along three transferring positions in such a way that the latent image forming positions and the transferring positions are situated at predetermined positions, respectively, in accordance with the circumference length of the drive roller of the photoconductor belt so as to prevent the misalignment of the color images on the record paper.
However, the above mentioned technique disclosed in the publication can not simply be applied to the color recording apparatus which forms a multicolored image by overlapping a plurality of different monochrome color images on a record paper which is reciprocated by a conveyor means. This is because that this kind of color recording apparatus has only one common transferring position where the plurality of different color images are transferred one after another by reciprocating the conveyor means instead of arranging a plurality of transferring positions corresponding to the different colors, respectively, therefore, the problem of the misalignment of the color toner images on the paper can not be obviated by the above mentioned prior art technique which aims to form each of a plurality of latent images precisely at a predetermined position on the photoconductor belt corresponding to the respective different color.
Also, for example, Japanese Unexamined Patent Publications Nos. 62-186282 and 62-118366 disclose another color copying apparatus which comprises an original support plate on which an original to be copied is placed and which plate is movable forward and backward and a conveyor belt which carries a record paper thereon and moves forward and backward wherein the original support plate and the conveyor belt are mechanically linked to be synchronized with each other. In accordance with this original moving type color copying apparatus, it becomes possible to obtain a clear color copy without misaligning the color components transferred on the paper since the record paper moves along with the original to be copied.
However, the above mentioned prior art technique disclosed in the publications can not be applied to a color printer which forms a color hard copy from a video signal transmitted from a TV system or an image scanner which is provided independently from the printer. Also, the prior art technique can not simply be utilized in the original scanning type color copying apparatus when a scaling system is in operation.
On the other hand, conventionally, it has been known various kinds of electrophotographic color copying apparatus which comprises a means for repeating the transferring operation of different monochrome color images to form a multicolored image from a plurality of different color images. For example, as such a image transfer repeating means, a transfer drum, a system comprising a plurality of photoconductors disposed in series and a switch back transferring system are known.
However, with respect to the transfer drum means, a hard paper such as a post card can not be used as a record paper since the record paper must be flexible enough to be wound around the drum. Also, the record paper requires a blank portion at an end of the paper for clamping the paper to the drum. Besides, the circumferential length of the drum must be longer than the length of the paper, which causes to enlarge the structure of the copying apparatus.
On the other hand, in accordance with the system comprising a plurality of photoconductors disposed in series, a relatively hard paper can be used and has an advantage that the copying operation can be carried out at a high speed. However, the provision of the plurality of photoconductors inevitably causes to enlarge the structure of the copying apparatus and increase the cost thereof.
Also, with respect to the switch back image transfer system which is disclosed for example in the Japanese Unexamined Patent Publication No. 62-118366, the length of the transferring belt is shortened and the leading edge and the trailing edge of the paper are separated from the drum in such a way that the edges are guided to a paper discharge tray and a paper feed cassette, respectively, which makes it possible to use a hard paper and print a color image on an entire area of the paper due to the structure thereof which also makes it possible to realize a compact structure and reduce the cost thereof. However, this structure has a disadvantage that the speed of the transfer belt in the backward motion thereof is the same as that in the forward motion thereof, which results in the reduction of the speed of the copying operation in comparison to the transfer drum means.
As mentioned above, the color recording apparatus comprising the switch back image transfer system has advantages that the system makes it possible to use a hard paper and print a color image on an entire area of the paper due to the structure thereof which also makes it possible to realize a compact structure and reduce the cost thereof, by constructing the structure in such a way that the length of the transferring belt is shortened and the leading edge and the trailing edge of the paper are separated from the drum in such a way that the edges are guided to a paper discharge tray and a paper feed cassette, respectively.
Although the switch back image transfer system has the above mentioned advantages, the system has a problem as described below. That is, the electrostatic latent image forming positions and the image transferring positions on the photoconductor belt are determined corresponding to one specific paper such as a largest standard size paper. Therefore, the operational speed of the apparatus is always the same irrespective of the size of the record paper so that the speed can not be heightened even when a paper of small size is used.